When an etching step is performed to form a fine pattern having a high aspect ratio on a semiconductor wafer, a cleaning step and a drying step are then performed to remove an impurity and a residue left on a surface of the semiconductor wafer. It is possible to suppress, by silylating a surface of the pattern in this cleaning step, collapse of the pattern in the drying step. In this case, the collapse margin can be widened by rinsing the semiconductor wafer with isopropyl alcohol (IPA) after the silylation and then spin-drying the semiconductor wafer. In many cases, the semiconductor wafer is also rinsed with the IPA before the silylation.
On the other hand, it is studied to silylate the semiconductor wafer in a batch treatment apparatus instead of a single-wafer treatment apparatus. However, if the silylation agent and the IPA are used in a liquid state in the batch treatment apparatus, amounts of using these chemicals are extremely large. Therefore, it is considered to reduce the amounts of using these chemicals by using the silylation agent and the IPA in a gas state (vapor state). In this case, the silylation agent and the IPA are liquefied on the surface of the semiconductor wafer to be attached to the semiconductor wafer, so that the semiconductor wafer can be wet. However, the silylation agent and the IPA attached to the semiconductor wafer are vaporized during the silylation, and therefore the semiconductor wafer is dried during the silylation. Accordingly, the pattern on the semiconductor wafer may collapse.